Today, in nearly one of every 10 U.S. counties, 303 of 3,141, more than half the residents are ethnic minorities, according to a new report from the Census Bureau.

In the 12 months ended June 30, 2006, two more major counties passed the 50 percent mark: Denver County in Colorado and Baton Rouge Parish (the equivalent of a county) in Louisiana. Each has a total population of more than 400,000 residents.

Los Angeles County, with nearly 10 million people, is the most heavily populated county in the United States by far and is also one of the most diverse. It has more minority residents than anywhere else. (See key stats on Los Angeles.)

According to the Census Bureau, Los Angeles County has some 7 million minority residents - 71 percent of its population and one of every 14 minority residents in the nation.

That's more people than the total population of the second biggest U.S. county, Cook, which includes Chicago. Los Angeles County has more minority residents than do each of 38 states have people of all ethnicities.

Although Hispanics dominate Los Angeles County's demographics, it also has nearly one million African-American residents, trailing only Cook County, which has 1.4 million. Los Angeles County also claims 1.4 million Asians - more than any other county.

A clear majority of Los Angeles County's population of 4.7 Hispanics is Mexican, but Central American nations such as Honduras, Guatemala and El Salvador are well represented.

The fastest growing county-wide minority population, numerically, was Harris County (Houston), where the minority population expanded by 121,400 during the 12 months. Its 2.5 million minority residents (63 percent of the county population) puts it in third place, right behind Cook, for diversity.

Texas has some counties that are nearly as Mexican as Mexico: border town Starr County is the most thoroughly Hispanic county in the country. About 97 percent of its nearly 62,000 residents are of Hispanic origin.

Claiborne County, Mississippi, has the highest percentage of African Americans of any county - 85 percent of about 11,500 people.

The Census Bureau release also included age data. It revealed that Florida unsurprisingly had four of the top 10 counties with the highest percentage of population 65 or older. Charlotte, on Florida's Gulf Coast, led all counties with 31.2 percent of its residents being senior citizens.

The younger set was represented by Colorado, Georgia and Alaska. They combined for seven of the top 10 counties with the lowest percentage of populations 65 or older. Leading the pack was Chattahoochee, Georgia, home of Fort Benning, with just 2.6 percent of its population elderly.

The county with the biggest proportion of very young children was Webb County, Texas (Laredo), where 13.1 percent of the population was under five years old. Webb is also one of the most heavily Hispanic counties around, with about 94 percent of its population being Latino.